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	$92.58	7.206%	$99.2513	$99.25	$99.25	$99.30
Purchase #2	$5.56	6.587%	$5.9262	$5.93	$5.95	$5.90
Purchase #3	$24.78	3.767%	$25.7135	$25.71	$25.70	$25.70
Purchase #4	$247.37	12.174%	$277.4848	$277.48	$277.50	$277.50
Purchase #5	$188.75	4.181%	$196.6416	$196.64	$196.65	$196.60
Purchase #6	$216.95	10.306%	$239.3089	$239.31	$239.30	$239.30
Purchase #7	$202.86	9.592%	$222.3183	$222.32	$222.30	$222.30
7 purchase totals =	$978.85		$1,066.6446	$1,066.64	$1,066.65	$1,066.60