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	$64.94	4.154%	$67.6376	$67.64	$67.65	$67.60
Purchase #2	$188.61	7.530%	$202.8123	$202.81	$202.80	$202.80
Purchase #3	$94.40	3.361%	$97.5728	$97.57	$97.55	$97.60
Purchase #4	$115.32	7.422%	$123.8791	$123.88	$123.90	$123.90
Purchase #5	$82.38	3.418%	$85.1957	$85.20	$85.20	$85.20
Purchase #6	$152.77	12.167%	$171.3575	$171.36	$171.35	$171.40
Purchase #7	$243.44	4.663%	$254.7916	$254.79	$254.80	$254.80
7 purchase totals =	$941.86		$1,003.2466	$1,003.25	$1,003.25	$1,003.30