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	$99.71	6.666%	$106.3567	$106.36	$106.35	$106.40
Purchase #2	$209.45	11.476%	$233.4865	$233.49	$233.50	$233.50
Purchase #3	$186.75	9.625%	$204.7247	$204.72	$204.70	$204.70
Purchase #4	$59.67	5.256%	$62.8063	$62.81	$62.80	$62.80
Purchase #5	$195.80	9.172%	$213.7588	$213.76	$213.75	$213.80
Purchase #6	$91.27	8.606%	$99.1247	$99.12	$99.10	$99.10
Purchase #7	$132.39	7.474%	$142.2848	$142.28	$142.30	$142.30
7 purchase totals =	$975.04		$1,062.5425	$1,062.54	$1,062.50	$1,062.60