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	$82.59	12.276%	$92.7287	$92.73	$92.75	$92.70
Purchase #2	$166.78	4.508%	$174.2984	$174.30	$174.30	$174.30
Purchase #3	$207.39	12.131%	$232.5485	$232.55	$232.55	$232.50
Purchase #4	$129.64	7.593%	$139.4836	$139.48	$139.50	$139.50
Purchase #5	$126.41	6.132%	$134.1615	$134.16	$134.15	$134.20
Purchase #6	$207.46	7.365%	$222.7394	$222.74	$222.75	$222.70
Purchase #7	$96.82	7.576%	$104.1551	$104.16	$104.15	$104.20
7 purchase totals =	$1,017.09		$1,100.1152	$1,100.12	$1,100.15	$1,100.10