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	$158.72	3.627%	$164.4768	$164.48	$164.50	$164.50
Purchase #2	$238.86	10.515%	$263.9761	$263.98	$264.00	$264.00
Purchase #3	$21.26	4.776%	$22.2754	$22.28	$22.30	$22.30
Purchase #4	$234.25	12.711%	$264.0255	$264.03	$264.05	$264.00
Purchase #5	$131.92	10.358%	$145.5843	$145.58	$145.60	$145.60
Purchase #6	$53.82	9.157%	$58.7483	$58.75	$58.75	$58.70
Purchase #7	$91.96	7.583%	$98.9333	$98.93	$98.95	$98.90
7 purchase totals =	$930.79		$1,018.0197	$1,018.03	$1,018.15	$1,018.00