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	$110.52	7.459%	$118.7637	$118.76	$118.75	$118.80
Purchase #2	$185.78	7.776%	$200.2263	$200.23	$200.25	$200.20
Purchase #3	$96.90	12.611%	$109.1201	$109.12	$109.10	$109.10
Purchase #4	$179.56	6.727%	$191.639	$191.64	$191.65	$191.60
Purchase #5	$225.74	4.534%	$235.9751	$235.98	$236.00	$236.00
Purchase #6	$139.34	12.207%	$156.3492	$156.35	$156.35	$156.30
Purchase #7	$49.67	7.450%	$53.3704	$53.37	$53.35	$53.40
7 purchase totals =	$987.51		$1,065.4438	$1,065.45	$1,065.45	$1,065.40