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	$61.54	6.279%	$65.4041	$65.40	$65.40	$65.40
Purchase #2	$79.45	12.413%	$89.3121	$89.31	$89.30	$89.30
Purchase #3	$53.97	5.294%	$56.8272	$56.83	$56.85	$56.80
Purchase #4	$109.75	4.202%	$114.3617	$114.36	$114.35	$114.40
Purchase #5	$219.52	10.655%	$242.9099	$242.91	$242.90	$242.90
Purchase #6	$142.41	11.436%	$158.696	$158.70	$158.70	$158.70
Purchase #7	$74.80	5.170%	$78.6672	$78.67	$78.65	$78.70
7 purchase totals =	$741.44		$806.1782	$806.18	$806.15	$806.20