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	$189.27	4.589%	$197.9556	$197.96	$197.95	$198.00
Purchase #2	$108.78	4.192%	$113.3401	$113.34	$113.35	$113.30
Purchase #3	$205.84	8.543%	$223.4249	$223.42	$223.40	$223.40
Purchase #4	$66.52	11.686%	$74.2935	$74.29	$74.30	$74.30
Purchase #5	$215.90	11.294%	$240.2837	$240.28	$240.30	$240.30
Purchase #6	$152.29	9.320%	$166.4834	$166.48	$166.50	$166.50
Purchase #7	$79.80	13.666%	$90.7055	$90.71	$90.70	$90.70
7 purchase totals =	$1,018.40		$1,106.4867	$1,106.48	$1,106.50	$1,106.50