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	$162.94	7.178%	$174.6358	$174.64	$174.65	$174.60
Purchase #2	$83.64	7.453%	$89.8737	$89.87	$89.85	$89.90
Purchase #3	$67.41	8.165%	$72.914	$72.91	$72.90	$72.90
Purchase #4	$121.71	7.274%	$130.5632	$130.56	$130.55	$130.60
Purchase #5	$18.58	12.529%	$20.9079	$20.91	$20.90	$20.90
Purchase #6	$250.82	4.586%	$262.3226	$262.32	$262.30	$262.30
Purchase #7	$68.68	5.794%	$72.6593	$72.66	$72.65	$72.70
7 purchase totals =	$773.78		$823.8765	$823.87	$823.80	$823.90