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	$207.79	10.873%	$230.383	$230.38	$230.40	$230.40
Purchase #2	$29.46	9.199%	$32.17	$32.17	$32.15	$32.20
Purchase #3	$44.35	10.368%	$48.9482	$48.95	$48.95	$48.90
Purchase #4	$238.70	10.112%	$262.8373	$262.84	$262.85	$262.80
Purchase #5	$180.36	8.760%	$196.1595	$196.16	$196.15	$196.20
Purchase #6	$33.88	13.836%	$38.5676	$38.57	$38.55	$38.60
Purchase #7	$243.51	10.132%	$268.1824	$268.18	$268.20	$268.20
7 purchase totals =	$978.05		$1,077.2480	$1,077.25	$1,077.25	$1,077.30