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	$181.96	7.399%	$195.4232	$195.42	$195.40	$195.40
Purchase #2	$216.89	12.438%	$243.8668	$243.87	$243.85	$243.90
Purchase #3	$197.77	3.596%	$204.8818	$204.88	$204.90	$204.90
Purchase #4	$6.47	6.699%	$6.9034	$6.90	$6.90	$6.90
Purchase #5	$184.74	3.442%	$191.0988	$191.10	$191.10	$191.10
Purchase #6	$45.74	11.216%	$50.8702	$50.87	$50.85	$50.90
Purchase #7	$152.75	10.166%	$168.2786	$168.28	$168.30	$168.30
7 purchase totals =	$986.32		$1,061.3228	$1,061.32	$1,061.30	$1,061.40