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	$101.78	10.309%	$112.2725	$112.27	$112.25	$112.30
Purchase #2	$83.25	5.826%	$88.1001	$88.10	$88.10	$88.10
Purchase #3	$198.38	9.260%	$216.75	$216.75	$216.75	$216.80
Purchase #4	$165.29	11.145%	$183.7116	$183.71	$183.70	$183.70
Purchase #5	$136.79	11.740%	$152.8491	$152.85	$152.85	$152.80
Purchase #6	$82.55	8.469%	$89.5412	$89.54	$89.55	$89.50
Purchase #7	$231.74	8.571%	$251.6024	$251.60	$251.60	$251.60
7 purchase totals =	$999.78		$1,094.8269	$1,094.82	$1,094.80	$1,094.80