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	$200.90	4.254%	$209.4463	$209.45	$209.45	$209.40
Purchase #2	$196.98	11.617%	$219.8632	$219.86	$219.85	$219.90
Purchase #3	$82.92	7.496%	$89.1357	$89.14	$89.15	$89.10
Purchase #4	$207.85	6.517%	$221.3956	$221.40	$221.40	$221.40
Purchase #5	$195.41	5.782%	$206.7086	$206.71	$206.70	$206.70
Purchase #6	$12.96	5.645%	$13.6916	$13.69	$13.70	$13.70
Purchase #7	$53.46	8.745%	$58.1351	$58.14	$58.15	$58.10
7 purchase totals =	$950.48		$1,018.3761	$1,018.39	$1,018.40	$1,018.30