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	$57.50	4.250%	$59.9438	$59.94	$59.95	$59.90
Purchase #2	$152.91	5.503%	$161.3246	$161.32	$161.30	$161.30
Purchase #3	$204.79	7.753%	$220.6674	$220.67	$220.65	$220.70
Purchase #4	$150.59	11.688%	$168.191	$168.19	$168.20	$168.20
Purchase #5	$79.63	13.419%	$90.3155	$90.32	$90.30	$90.30
Purchase #6	$147.84	11.390%	$164.679	$164.68	$164.70	$164.70
Purchase #7	$149.73	4.200%	$156.0187	$156.02	$156.00	$156.00
7 purchase totals =	$942.99		$1,021.1400	$1,021.14	$1,021.10	$1,021.10