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	$202.78	3.381%	$209.636	$209.64	$209.65	$209.60
Purchase #2	$146.33	13.219%	$165.6734	$165.67	$165.65	$165.70
Purchase #3	$231.36	8.197%	$250.3246	$250.32	$250.30	$250.30
Purchase #4	$229.91	6.705%	$245.3255	$245.33	$245.35	$245.30
Purchase #5	$53.81	6.418%	$57.2635	$57.26	$57.25	$57.30
Purchase #6	$88.49	5.481%	$93.3401	$93.34	$93.35	$93.30
Purchase #7	$84.81	6.530%	$90.3481	$90.35	$90.35	$90.30
7 purchase totals =	$1,037.49		$1,111.9112	$1,111.91	$1,111.90	$1,111.80