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	$55.88	12.288%	$62.7465	$62.75	$62.75	$62.70
Purchase #2	$194.79	10.800%	$215.8273	$215.83	$215.85	$215.80
Purchase #3	$99.56	6.820%	$106.35	$106.35	$106.35	$106.40
Purchase #4	$103.70	7.656%	$111.6393	$111.64	$111.65	$111.60
Purchase #5	$170.94	7.780%	$184.2391	$184.24	$184.25	$184.20
Purchase #6	$147.43	6.209%	$156.5839	$156.58	$156.60	$156.60
Purchase #7	$162.89	10.125%	$179.3826	$179.38	$179.40	$179.40
7 purchase totals =	$935.19		$1,016.7687	$1,016.77	$1,016.85	$1,016.70