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	$110.83	5.347%	$116.7561	$116.76	$116.75	$116.80
Purchase #2	$88.77	3.140%	$91.5574	$91.56	$91.55	$91.60
Purchase #3	$197.95	6.788%	$211.3868	$211.39	$211.40	$211.40
Purchase #4	$170.81	8.782%	$185.8105	$185.81	$185.80	$185.80
Purchase #5	$66.78	5.802%	$70.6546	$70.65	$70.65	$70.70
Purchase #6	$68.83	10.321%	$75.9339	$75.93	$75.95	$75.90
Purchase #7	$180.86	8.543%	$196.3109	$196.31	$196.30	$196.30
7 purchase totals =	$884.83		$948.4102	$948.41	$948.40	$948.50