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	$173.35	12.550%	$195.1054	$195.11	$195.10	$195.10
Purchase #2	$13.28	3.610%	$13.7594	$13.76	$13.75	$13.80
Purchase #3	$232.36	11.627%	$259.3765	$259.38	$259.40	$259.40
Purchase #4	$187.38	6.807%	$200.135	$200.14	$200.15	$200.10
Purchase #5	$84.37	5.854%	$89.309	$89.31	$89.30	$89.30
Purchase #6	$98.73	7.724%	$106.3559	$106.36	$106.35	$106.40
Purchase #7	$71.69	9.692%	$78.6382	$78.64	$78.65	$78.60
7 purchase totals =	$861.16		$942.6794	$942.70	$942.70	$942.70