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	$55.56	10.687%	$61.4977	$61.50	$61.50	$61.50
Purchase #2	$64.87	5.258%	$68.2809	$68.28	$68.30	$68.30
Purchase #3	$179.53	4.793%	$188.1349	$188.13	$188.15	$188.10
Purchase #4	$182.64	7.617%	$196.5517	$196.55	$196.55	$196.60
Purchase #5	$242.76	9.211%	$265.1206	$265.12	$265.10	$265.10
Purchase #6	$56.86	4.728%	$59.5483	$59.55	$59.55	$59.50
Purchase #7	$75.92	12.190%	$85.1746	$85.17	$85.15	$85.20
7 purchase totals =	$858.14		$924.3087	$924.30	$924.30	$924.30