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	$80.57	7.681%	$86.7586	$86.76	$86.75	$86.80
Purchase #2	$115.61	7.744%	$124.5628	$124.56	$124.55	$124.60
Purchase #3	$90.92	9.354%	$99.4247	$99.42	$99.40	$99.40
Purchase #4	$153.51	12.818%	$173.1869	$173.19	$173.20	$173.20
Purchase #5	$89.55	11.173%	$99.5554	$99.56	$99.55	$99.60
Purchase #6	$31.78	7.158%	$34.0548	$34.05	$34.05	$34.10
Purchase #7	$184.78	6.161%	$196.1643	$196.16	$196.15	$196.20
7 purchase totals =	$746.72		$813.7075	$813.70	$813.65	$813.90