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	$188.72	3.247%	$194.8477	$194.85	$194.85	$194.80
Purchase #2	$151.63	4.785%	$158.8855	$158.89	$158.90	$158.90
Purchase #3	$186.52	7.773%	$201.0182	$201.02	$201.00	$201.00
Purchase #4	$86.34	6.301%	$91.7803	$91.78	$91.80	$91.80
Purchase #5	$72.82	7.148%	$78.0252	$78.03	$78.05	$78.00
Purchase #6	$31.92	4.276%	$33.2849	$33.28	$33.30	$33.30
Purchase #7	$185.36	3.279%	$191.438	$191.44	$191.45	$191.40
7 purchase totals =	$903.31		$949.2798	$949.29	$949.35	$949.20