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	$114.55	3.568%	$118.6371	$118.64	$118.65	$118.60
Purchase #2	$47.59	13.785%	$54.1503	$54.15	$54.15	$54.20
Purchase #3	$80.42	12.212%	$90.2409	$90.24	$90.25	$90.20
Purchase #4	$48.41	10.288%	$53.3904	$53.39	$53.40	$53.40
Purchase #5	$7.44	6.477%	$7.9219	$7.92	$7.90	$7.90
Purchase #6	$56.68	13.379%	$64.2632	$64.26	$64.25	$64.30
Purchase #7	$51.67	6.656%	$55.1092	$55.11	$55.10	$55.10
7 purchase totals =	$406.76		$443.7130	$443.71	$443.70	$443.70