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	$89.78	7.511%	$96.5234	$96.52	$96.50	$96.50
Purchase #2	$221.90	9.558%	$243.1092	$243.11	$243.10	$243.10
Purchase #3	$243.86	5.279%	$256.7334	$256.73	$256.75	$256.70
Purchase #4	$135.66	4.524%	$141.7973	$141.80	$141.80	$141.80
Purchase #5	$191.29	9.579%	$209.6137	$209.61	$209.60	$209.60
Purchase #6	$29.31	6.645%	$31.2576	$31.26	$31.25	$31.30
Purchase #7	$222.46	11.737%	$248.5701	$248.57	$248.55	$248.60
7 purchase totals =	$1,134.26		$1,227.6047	$1,227.60	$1,227.55	$1,227.60