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	$104.69	10.155%	$115.3213	$115.32	$115.30	$115.30
Purchase #2	$181.91	8.102%	$196.6483	$196.65	$196.65	$196.60
Purchase #3	$172.77	10.829%	$191.4793	$191.48	$191.50	$191.50
Purchase #4	$65.60	3.211%	$67.7064	$67.71	$67.70	$67.70
Purchase #5	$173.59	5.349%	$182.8753	$182.88	$182.90	$182.90
Purchase #6	$245.63	12.822%	$277.1247	$277.12	$277.10	$277.10
Purchase #7	$20.25	12.362%	$22.7533	$22.75	$22.75	$22.80
7 purchase totals =	$964.44		$1,053.9086	$1,053.91	$1,053.90	$1,053.90