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	$30.62	3.688%	$31.7493	$31.75	$31.75	$31.70
Purchase #2	$77.95	4.200%	$81.2239	$81.22	$81.20	$81.20
Purchase #3	$116.48	9.270%	$127.2777	$127.28	$127.30	$127.30
Purchase #4	$33.97	4.557%	$35.518	$35.52	$35.50	$35.50
Purchase #5	$205.73	8.749%	$223.7293	$223.73	$223.75	$223.70
Purchase #6	$130.69	8.435%	$141.7137	$141.71	$141.70	$141.70
Purchase #7	$174.47	12.398%	$196.1008	$196.10	$196.10	$196.10
7 purchase totals =	$769.91		$837.3127	$837.31	$837.30	$837.20