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	$52.64	3.874%	$54.6793	$54.68	$54.70	$54.70
Purchase #2	$110.38	5.191%	$116.1098	$116.11	$116.10	$116.10
Purchase #3	$120.99	11.399%	$134.7817	$134.78	$134.80	$134.80
Purchase #4	$185.72	8.144%	$200.845	$200.85	$200.85	$200.80
Purchase #5	$28.79	8.784%	$31.3189	$31.32	$31.30	$31.30
Purchase #6	$111.49	3.734%	$115.653	$115.65	$115.65	$115.70
Purchase #7	$129.50	7.703%	$139.4754	$139.48	$139.50	$139.50
7 purchase totals =	$739.51		$792.8631	$792.87	$792.90	$792.90