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	$221.81	7.274%	$237.9445	$237.94	$237.95	$237.90
Purchase #2	$62.56	4.391%	$65.307	$65.31	$65.30	$65.30
Purchase #3	$136.83	9.782%	$150.2147	$150.21	$150.20	$150.20
Purchase #4	$85.33	7.697%	$91.8979	$91.90	$91.90	$91.90
Purchase #5	$244.48	9.641%	$268.0503	$268.05	$268.05	$268.10
Purchase #6	$28.91	13.827%	$32.9074	$32.91	$32.90	$32.90
Purchase #7	$155.63	7.227%	$166.8774	$166.88	$166.90	$166.90
7 purchase totals =	$935.55		$1,013.1992	$1,013.20	$1,013.20	$1,013.20