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	$68.53	5.546%	$72.3307	$72.33	$72.35	$72.30
Purchase #2	$157.48	10.574%	$174.1319	$174.13	$174.15	$174.10
Purchase #3	$75.52	10.600%	$83.5251	$83.53	$83.55	$83.50
Purchase #4	$43.85	10.621%	$48.5073	$48.51	$48.50	$48.50
Purchase #5	$42.61	11.140%	$47.3568	$47.36	$47.35	$47.40
Purchase #6	$196.59	11.557%	$219.3099	$219.31	$219.30	$219.30
Purchase #7	$140.27	8.731%	$152.517	$152.52	$152.50	$152.50
7 purchase totals =	$724.85		$797.6787	$797.69	$797.70	$797.60