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	$105.77	6.150%	$112.2749	$112.27	$112.25	$112.30
Purchase #2	$74.45	8.302%	$80.6308	$80.63	$80.65	$80.60
Purchase #3	$231.81	9.512%	$253.8598	$253.86	$253.85	$253.90
Purchase #4	$110.62	11.214%	$123.0249	$123.02	$123.00	$123.00
Purchase #5	$229.88	13.164%	$260.1414	$260.14	$260.15	$260.10
Purchase #6	$99.30	12.417%	$111.6301	$111.63	$111.65	$111.60
Purchase #7	$110.30	9.279%	$120.5347	$120.53	$120.55	$120.50
7 purchase totals =	$962.13		$1,062.0966	$1,062.08	$1,062.10	$1,062.00