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	$180.86	11.515%	$201.686	$201.69	$201.70	$201.70
Purchase #2	$96.66	7.138%	$103.5596	$103.56	$103.55	$103.60
Purchase #3	$199.73	11.794%	$223.2862	$223.29	$223.30	$223.30
Purchase #4	$168.89	8.532%	$183.2997	$183.30	$183.30	$183.30
Purchase #5	$192.59	4.740%	$201.7188	$201.72	$201.70	$201.70
Purchase #6	$73.49	7.175%	$78.7629	$78.76	$78.75	$78.80
Purchase #7	$104.39	3.753%	$108.3078	$108.31	$108.30	$108.30
7 purchase totals =	$1,016.61		$1,100.6210	$1,100.63	$1,100.60	$1,100.70