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	$215.38	3.200%	$222.2722	$222.27	$222.25	$222.30
Purchase #2	$31.84	4.579%	$33.298	$33.30	$33.30	$33.30
Purchase #3	$102.63	11.383%	$114.3124	$114.31	$114.30	$114.30
Purchase #4	$41.73	9.107%	$45.5304	$45.53	$45.55	$45.50
Purchase #5	$177.72	6.227%	$188.7866	$188.79	$188.80	$188.80
Purchase #6	$133.83	6.225%	$142.1609	$142.16	$142.15	$142.20
Purchase #7	$154.79	9.664%	$169.7489	$169.75	$169.75	$169.70
7 purchase totals =	$857.92		$916.1094	$916.11	$916.10	$916.10