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	$153.86	11.180%	$171.0615	$171.06	$171.05	$171.10
Purchase #2	$54.96	13.635%	$62.4538	$62.45	$62.45	$62.50
Purchase #3	$62.47	3.281%	$64.5196	$64.52	$64.50	$64.50
Purchase #4	$142.92	12.444%	$160.705	$160.71	$160.70	$160.70
Purchase #5	$53.91	7.515%	$57.9613	$57.96	$57.95	$58.00
Purchase #6	$94.86	9.236%	$103.6213	$103.62	$103.60	$103.60
Purchase #7	$148.53	3.708%	$154.0375	$154.04	$154.05	$154.00
7 purchase totals =	$711.51		$774.3600	$774.36	$774.30	$774.40