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	$194.86	7.298%	$209.0809	$209.08	$209.10	$209.10
Purchase #2	$94.90	4.413%	$99.0879	$99.09	$99.10	$99.10
Purchase #3	$169.93	10.372%	$187.5551	$187.56	$187.55	$187.60
Purchase #4	$151.42	10.364%	$167.1132	$167.11	$167.10	$167.10
Purchase #5	$168.86	11.809%	$188.8007	$188.80	$188.80	$188.80
Purchase #6	$167.51	4.659%	$175.3143	$175.31	$175.30	$175.30
Purchase #7	$247.36	10.501%	$273.3353	$273.34	$273.35	$273.30
7 purchase totals =	$1,194.84		$1,300.2874	$1,300.29	$1,300.30	$1,300.30