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	$110.73	5.704%	$117.046	$117.05	$117.05	$117.00
Purchase #2	$189.73	5.799%	$200.7324	$200.73	$200.75	$200.70
Purchase #3	$174.82	12.252%	$196.2389	$196.24	$196.25	$196.20
Purchase #4	$115.32	9.283%	$126.0252	$126.03	$126.05	$126.00
Purchase #5	$133.48	8.839%	$145.2783	$145.28	$145.30	$145.30
Purchase #6	$59.79	9.191%	$65.2853	$65.29	$65.30	$65.30
Purchase #7	$33.67	12.468%	$37.868	$37.87	$37.85	$37.90
7 purchase totals =	$817.54		$888.4741	$888.49	$888.55	$888.40