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	$100.68	4.544%	$105.2549	$105.25	$105.25	$105.30
Purchase #2	$239.82	12.454%	$269.6872	$269.69	$269.70	$269.70
Purchase #3	$62.59	5.604%	$66.0975	$66.10	$66.10	$66.10
Purchase #4	$244.50	10.610%	$270.4415	$270.44	$270.45	$270.40
Purchase #5	$80.81	10.323%	$89.152	$89.15	$89.15	$89.20
Purchase #6	$181.51	10.373%	$200.338	$200.34	$200.35	$200.30
Purchase #7	$47.85	7.190%	$51.2904	$51.29	$51.30	$51.30
7 purchase totals =	$957.76		$1,052.2615	$1,052.26	$1,052.30	$1,052.30