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	$175.80	11.501%	$196.0188	$196.02	$196.00	$196.00
Purchase #2	$167.31	12.570%	$188.3409	$188.34	$188.35	$188.30
Purchase #3	$31.96	9.861%	$35.1116	$35.11	$35.10	$35.10
Purchase #4	$98.63	12.576%	$111.0337	$111.03	$111.05	$111.00
Purchase #5	$48.92	7.575%	$52.6257	$52.63	$52.65	$52.60
Purchase #6	$158.98	13.860%	$181.0146	$181.01	$181.00	$181.00
Purchase #7	$58.61	3.635%	$60.7405	$60.74	$60.75	$60.70
7 purchase totals =	$740.21		$824.8858	$824.88	$824.90	$824.70