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	$234.98	6.838%	$251.0479	$251.05	$251.05	$251.00
Purchase #2	$82.37	3.315%	$85.1006	$85.10	$85.10	$85.10
Purchase #3	$75.79	3.490%	$78.4351	$78.44	$78.45	$78.40
Purchase #4	$52.46	9.209%	$57.291	$57.29	$57.30	$57.30
Purchase #5	$79.81	11.745%	$89.1837	$89.18	$89.20	$89.20
Purchase #6	$179.32	10.645%	$198.4086	$198.41	$198.40	$198.40
Purchase #7	$166.27	4.212%	$173.2733	$173.27	$173.25	$173.30
7 purchase totals =	$871.00		$932.7402	$932.74	$932.75	$932.70