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	$177.59	7.686%	$191.2396	$191.24	$191.25	$191.20
Purchase #2	$221.40	4.658%	$231.7128	$231.71	$231.70	$231.70
Purchase #3	$69.69	4.796%	$73.0323	$73.03	$73.05	$73.00
Purchase #4	$163.73	5.133%	$172.1343	$172.13	$172.15	$172.10
Purchase #5	$235.70	12.399%	$264.9244	$264.92	$264.90	$264.90
Purchase #6	$75.30	3.812%	$78.1704	$78.17	$78.15	$78.20
Purchase #7	$106.33	5.360%	$112.0293	$112.03	$112.05	$112.00
7 purchase totals =	$1,049.74		$1,123.2431	$1,123.23	$1,123.25	$1,123.10