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	$162.76	7.496%	$174.9605	$174.96	$174.95	$175.00
Purchase #2	$54.81	3.127%	$56.5239	$56.52	$56.50	$56.50
Purchase #3	$131.31	10.202%	$144.7062	$144.71	$144.70	$144.70
Purchase #4	$72.70	11.267%	$80.8911	$80.89	$80.90	$80.90
Purchase #5	$45.69	5.298%	$48.1107	$48.11	$48.10	$48.10
Purchase #6	$230.75	6.560%	$245.8872	$245.89	$245.90	$245.90
Purchase #7	$238.25	11.107%	$264.7124	$264.71	$264.70	$264.70
7 purchase totals =	$936.27		$1,015.7920	$1,015.79	$1,015.75	$1,015.80