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	$167.41	12.761%	$188.7732	$188.77	$188.75	$188.80
Purchase #2	$176.67	10.423%	$195.0843	$195.08	$195.10	$195.10
Purchase #3	$84.82	6.769%	$90.5615	$90.56	$90.55	$90.60
Purchase #4	$81.32	10.559%	$89.9066	$89.91	$89.90	$89.90
Purchase #5	$25.88	4.424%	$27.0249	$27.02	$27.00	$27.00
Purchase #6	$223.98	7.278%	$240.2813	$240.28	$240.30	$240.30
Purchase #7	$146.97	12.472%	$165.3001	$165.30	$165.30	$165.30
7 purchase totals =	$907.05		$996.9319	$996.92	$996.90	$997.00