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	$48.69	7.529%	$52.3559	$52.36	$52.35	$52.40
Purchase #2	$115.63	13.859%	$131.6552	$131.66	$131.65	$131.70
Purchase #3	$189.76	3.468%	$196.3409	$196.34	$196.35	$196.30
Purchase #4	$220.78	7.872%	$238.1598	$238.16	$238.15	$238.20
Purchase #5	$243.58	6.693%	$259.8828	$259.88	$259.90	$259.90
Purchase #6	$93.72	10.362%	$103.4313	$103.43	$103.45	$103.40
Purchase #7	$35.35	13.599%	$40.1572	$40.16	$40.15	$40.20
7 purchase totals =	$947.51		$1,021.9831	$1,021.99	$1,022.00	$1,022.10