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	$240.87	11.721%	$269.1024	$269.10	$269.10	$269.10
Purchase #2	$191.85	12.358%	$215.5588	$215.56	$215.55	$215.60
Purchase #3	$194.37	7.454%	$208.8583	$208.86	$208.85	$208.90
Purchase #4	$80.52	7.721%	$86.7369	$86.74	$86.75	$86.70
Purchase #5	$171.33	12.596%	$192.9107	$192.91	$192.90	$192.90
Purchase #6	$46.66	4.832%	$48.9146	$48.91	$48.90	$48.90
Purchase #7	$84.73	6.282%	$90.0527	$90.05	$90.05	$90.10
7 purchase totals =	$1,010.33		$1,112.1344	$1,112.13	$1,112.10	$1,112.20