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	$79.74	13.363%	$90.3957	$90.40	$90.40	$90.40
Purchase #2	$157.70	13.591%	$179.133	$179.13	$179.15	$179.10
Purchase #3	$218.48	7.760%	$235.434	$235.43	$235.45	$235.40
Purchase #4	$239.64	7.436%	$257.4596	$257.46	$257.45	$257.50
Purchase #5	$95.76	3.690%	$99.2935	$99.29	$99.30	$99.30
Purchase #6	$106.63	5.436%	$112.4264	$112.43	$112.45	$112.40
Purchase #7	$130.54	4.807%	$136.8151	$136.82	$136.80	$136.80
7 purchase totals =	$1,028.49		$1,110.9573	$1,110.96	$1,111.00	$1,110.90