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	$183.70	5.662%	$194.1011	$194.10	$194.10	$194.10
Purchase #2	$218.96	12.249%	$245.7804	$245.78	$245.80	$245.80
Purchase #3	$145.59	4.843%	$152.6409	$152.64	$152.65	$152.60
Purchase #4	$93.82	4.778%	$98.3027	$98.30	$98.30	$98.30
Purchase #5	$247.82	6.628%	$264.2455	$264.25	$264.25	$264.20
Purchase #6	$42.52	13.251%	$48.1543	$48.15	$48.15	$48.20
Purchase #7	$108.53	13.713%	$123.4127	$123.41	$123.40	$123.40
7 purchase totals =	$1,040.94		$1,126.6376	$1,126.63	$1,126.65	$1,126.60