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	$80.86	6.553%	$86.1588	$86.16	$86.15	$86.20
Purchase #2	$152.44	12.737%	$171.8563	$171.86	$171.85	$171.90
Purchase #3	$59.98	7.281%	$64.3471	$64.35	$64.35	$64.30
Purchase #4	$155.54	7.657%	$167.4497	$167.45	$167.45	$167.40
Purchase #5	$223.38	4.455%	$233.3316	$233.33	$233.35	$233.30
Purchase #6	$208.88	10.739%	$231.3116	$231.31	$231.30	$231.30
Purchase #7	$46.57	5.403%	$49.0862	$49.09	$49.10	$49.10
7 purchase totals =	$927.65		$1,003.5413	$1,003.55	$1,003.55	$1,003.50