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	$169.39	10.818%	$187.7146	$187.71	$187.70	$187.70
Purchase #2	$31.33	8.118%	$33.8734	$33.87	$33.85	$33.90
Purchase #3	$202.49	4.138%	$210.869	$210.87	$210.85	$210.90
Purchase #4	$220.33	3.420%	$227.8653	$227.87	$227.85	$227.90
Purchase #5	$209.26	9.522%	$229.1857	$229.19	$229.20	$229.20
Purchase #6	$46.87	11.414%	$52.2197	$52.22	$52.20	$52.20
Purchase #7	$75.42	3.749%	$78.2475	$78.25	$78.25	$78.20
7 purchase totals =	$955.09		$1,019.9752	$1,019.98	$1,019.90	$1,020.00