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	$236.38	6.111%	$250.8252	$250.83	$250.85	$250.80
Purchase #2	$138.66	6.826%	$148.1249	$148.12	$148.10	$148.10
Purchase #3	$29.92	11.390%	$33.3279	$33.33	$33.35	$33.30
Purchase #4	$226.45	7.646%	$243.7644	$243.76	$243.75	$243.80
Purchase #5	$115.48	7.623%	$124.283	$124.28	$124.30	$124.30
Purchase #6	$142.72	6.574%	$152.1024	$152.10	$152.10	$152.10
Purchase #7	$137.25	11.407%	$152.9061	$152.91	$152.90	$152.90
7 purchase totals =	$1,026.86		$1,105.3339	$1,105.33	$1,105.35	$1,105.30