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	$142.78	7.863%	$154.0068	$154.01	$154.00	$154.00
Purchase #2	$222.30	6.156%	$235.9848	$235.98	$236.00	$236.00
Purchase #3	$7.32	12.477%	$8.2333	$8.23	$8.25	$8.20
Purchase #4	$121.84	4.543%	$127.3752	$127.38	$127.40	$127.40
Purchase #5	$197.85	12.396%	$222.3755	$222.38	$222.40	$222.40
Purchase #6	$35.81	4.242%	$37.3291	$37.33	$37.35	$37.30
Purchase #7	$110.40	7.575%	$118.7628	$118.76	$118.75	$118.80
7 purchase totals =	$838.30		$904.0675	$904.07	$904.15	$904.10