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	$68.46	5.803%	$72.4327	$72.43	$72.45	$72.40
Purchase #2	$96.60	7.849%	$104.1821	$104.18	$104.20	$104.20
Purchase #3	$132.27	7.805%	$142.5937	$142.59	$142.60	$142.60
Purchase #4	$30.86	11.191%	$34.3135	$34.31	$34.30	$34.30
Purchase #5	$234.39	12.764%	$264.3075	$264.31	$264.30	$264.30
Purchase #6	$95.86	6.580%	$102.1676	$102.17	$102.15	$102.20
Purchase #7	$13.46	6.445%	$14.3275	$14.33	$14.35	$14.30
7 purchase totals =	$671.90		$734.3246	$734.32	$734.35	$734.30