Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$109.27	4.217%	$113.8779	$113.88	$113.90	$113.90
Purchase #2	$194.26	4.677%	$203.3455	$203.35	$203.35	$203.30
Purchase #3	$99.69	11.515%	$111.1693	$111.17	$111.15	$111.20
Purchase #4	$149.45	10.701%	$165.4426	$165.44	$165.45	$165.40
Purchase #5	$179.38	4.635%	$187.6943	$187.69	$187.70	$187.70
Purchase #6	$181.75	10.520%	$200.8701	$200.87	$200.85	$200.90
Purchase #7	$168.88	11.473%	$188.2556	$188.26	$188.25	$188.30
7 purchase totals =	$1,082.68		$1,170.6553	$1,170.66	$1,170.65	$1,170.70