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	$71.34	9.538%	$78.1444	$78.14	$78.15	$78.10
Purchase #2	$191.59	11.541%	$213.7014	$213.70	$213.70	$213.70
Purchase #3	$81.78	4.340%	$85.3293	$85.33	$85.35	$85.30
Purchase #4	$200.51	7.467%	$215.4821	$215.48	$215.50	$215.50
Purchase #5	$213.98	13.717%	$243.3316	$243.33	$243.35	$243.30
Purchase #6	$156.30	5.716%	$165.2341	$165.23	$165.25	$165.20
Purchase #7	$47.38	11.726%	$52.9358	$52.94	$52.95	$52.90
7 purchase totals =	$962.88		$1,054.1587	$1,054.15	$1,054.25	$1,054.00