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	$145.70	5.806%	$154.1593	$154.16	$154.15	$154.20
Purchase #2	$156.82	6.776%	$167.4461	$167.45	$167.45	$167.40
Purchase #3	$229.74	3.298%	$237.3168	$237.32	$237.30	$237.30
Purchase #4	$80.45	12.369%	$90.4009	$90.40	$90.40	$90.40
Purchase #5	$171.45	10.418%	$189.3117	$189.31	$189.30	$189.30
Purchase #6	$191.71	9.243%	$209.4298	$209.43	$209.45	$209.40
Purchase #7	$180.82	13.755%	$205.6918	$205.69	$205.70	$205.70
7 purchase totals =	$1,156.69		$1,253.7564	$1,253.76	$1,253.75	$1,253.70