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	$175.42	5.530%	$185.1207	$185.12	$185.10	$185.10
Purchase #2	$245.64	6.645%	$261.9628	$261.96	$261.95	$262.00
Purchase #3	$186.87	6.694%	$199.3791	$199.38	$199.40	$199.40
Purchase #4	$210.97	12.839%	$238.0564	$238.06	$238.05	$238.10
Purchase #5	$123.72	5.780%	$130.871	$130.87	$130.85	$130.90
Purchase #6	$17.92	13.165%	$20.2792	$20.28	$20.30	$20.30
Purchase #7	$84.97	5.332%	$89.5006	$89.50	$89.50	$89.50
7 purchase totals =	$1,045.51		$1,125.1698	$1,125.17	$1,125.15	$1,125.30