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	$188.31	5.260%	$198.2151	$198.22	$198.20	$198.20
Purchase #2	$172.64	7.786%	$186.0818	$186.08	$186.10	$186.10
Purchase #3	$247.85	12.209%	$278.11	$278.11	$278.10	$278.10
Purchase #4	$167.55	10.518%	$185.1729	$185.17	$185.15	$185.20
Purchase #5	$85.33	4.837%	$89.4574	$89.46	$89.45	$89.50
Purchase #6	$52.58	7.207%	$56.3694	$56.37	$56.35	$56.40
Purchase #7	$152.30	5.267%	$160.3216	$160.32	$160.30	$160.30
7 purchase totals =	$1,066.56		$1,153.7282	$1,153.73	$1,153.65	$1,153.80