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	$31.89	11.341%	$35.5066	$35.51	$35.50	$35.50
Purchase #2	$193.28	8.811%	$210.3099	$210.31	$210.30	$210.30
Purchase #3	$229.46	3.635%	$237.8009	$237.80	$237.80	$237.80
Purchase #4	$62.69	3.438%	$64.8453	$64.85	$64.85	$64.80
Purchase #5	$42.90	7.614%	$46.1664	$46.17	$46.15	$46.20
Purchase #6	$198.70	6.360%	$211.3373	$211.34	$211.35	$211.30
Purchase #7	$64.69	11.743%	$72.2865	$72.29	$72.30	$72.30
7 purchase totals =	$823.61		$878.2529	$878.27	$878.25	$878.20