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	$195.95	6.682%	$209.0434	$209.04	$209.05	$209.00
Purchase #2	$159.98	4.409%	$167.0335	$167.03	$167.05	$167.00
Purchase #3	$198.37	11.179%	$220.5458	$220.55	$220.55	$220.50
Purchase #4	$72.76	13.859%	$82.8438	$82.84	$82.85	$82.80
Purchase #5	$170.78	10.298%	$188.3669	$188.37	$188.35	$188.40
Purchase #6	$156.32	7.320%	$167.7626	$167.76	$167.75	$167.80
Purchase #7	$33.31	13.729%	$37.8831	$37.88	$37.90	$37.90
7 purchase totals =	$987.47		$1,073.4791	$1,073.47	$1,073.50	$1,073.40