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	$187.54	4.417%	$195.8236	$195.82	$195.80	$195.80
Purchase #2	$92.37	6.297%	$98.1865	$98.19	$98.20	$98.20
Purchase #3	$152.36	6.480%	$162.2329	$162.23	$162.25	$162.20
Purchase #4	$40.59	3.693%	$42.089	$42.09	$42.10	$42.10
Purchase #5	$178.54	3.700%	$185.146	$185.15	$185.15	$185.10
Purchase #6	$11.51	12.200%	$12.9142	$12.91	$12.90	$12.90
Purchase #7	$81.74	4.116%	$85.1044	$85.10	$85.10	$85.10
7 purchase totals =	$744.65		$781.4966	$781.49	$781.50	$781.40