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	$98.58	5.737%	$104.2355	$104.24	$104.25	$104.20
Purchase #2	$120.92	9.768%	$132.7315	$132.73	$132.75	$132.70
Purchase #3	$55.65	6.239%	$59.122	$59.12	$59.10	$59.10
Purchase #4	$135.64	4.514%	$141.7628	$141.76	$141.75	$141.80
Purchase #5	$185.90	5.531%	$196.1821	$196.18	$196.20	$196.20
Purchase #6	$110.86	6.104%	$117.6269	$117.63	$117.65	$117.60
Purchase #7	$144.80	7.431%	$155.5601	$155.56	$155.55	$155.60
7 purchase totals =	$852.35		$907.2209	$907.22	$907.25	$907.20